Front Left Wheel unscrews itself

[Dom]

Hi. Been running my S400 for a few months now and have only just started seeing a strange problem with it.

I run 5-cell modified, and last weekend about half-way through 3 consecutive races, it managed to unscrew the nut from front left wheel, with it spectacularily flying off! It happened to a couple of other Serpent drivers in Modified.

I put it down to first my own mistake, not tightening the wheels properly.
Then I thought it might be the wheels - I changed them for an entirely different set for the third run.

I've been told what it might be, but looking to get other confirmation of the solution and see if it's a common problem and take it back to Serpent if it is.

The car is standard, except I'm running a gear diff at the back with 3000 cst oil in it and 0.6mm shims up front.

[l-u-k-e]

Hi. Been running my S400 for a few months now and have only just started seeing a strange problem with it.

I run 5-cell modified, and last weekend about half-way through 3 consecutive races, it managed to unscrew the nut from front left wheel, with it spectacularily flying off! It happened to a couple of other Serpent drivers in Modified.

I put it down to first my own mistake, not tightening the wheels properly.
Then I thought it might be the wheels - I changed them for an entirely different set for the third run.

I've been told what it might be, but looking to get other confirmation of the solution and see if it's a common problem and take it back to Serpent if it is.

The car is standard, except I'm running a gear diff at the back with 3000 cst oil in it and 0.6mm shims up front.

Alot of people i know have had this problem and all they did to solve it is put nylon nuts instead of the serrated nuts!

HTH
Luke

[Dom]

Thanks for the update.

In the 3rd run I tried a 4mm nylock nut but it did the same.
I guess it may have been old, and not as grippy as a new one.
I'll try and get some new ones and give them a go.

My original post wasn't very well worded. Apologies.

I'm curious to hear if other people are having the problem, and if so, does anyone have a theory on why it is happening.

I suspect it's because of the spool, and I'm going to consider running a diff up front. At least it'll help the front tyres!

[IanB]

I run 5-cell modified, and last weekend about half-way through 3 consecutive races, it managed to unscrew the nut from front left wheel, with it spectacularily flying off! It happened to a couple of other Serpent drivers in Modified.


Yes it has been known before , however it is normally the right front that comes loose.
You dont say what tyres and wheels you were using , wasnt sorex by any chance?

Luke is right , you use a flanged nylock nut on the front , there are also some different wheel hex's that are machined differently that help.

[l-u-k-e]

Yes it has been known before , however it is normally the right front that comes loose.
You dont say what tyres and wheels you were using , wasnt sorex by any chance?

Luke is right , you use a flanged nylock nut on the front , there are also some different wheel hex's that are machined differently that help.


Maybe this track goes the other way round which means it would change sides! Im guessing its the inside wheel that is coming off!

Or is that a silly suggestion?

[timmay langdell]

its because of the hex twisting in the wheel under accelleration and braking, tamiya wheel hexs seemed to sort this prob :)

[paul.upton]

Ive been running the S400 for a while now and not had any problems with kit hexes and kit wheel nuts, i just make sure that they are really tight!!

Paul

[terryh]

I had the same problem and each time it happened, one of the wheel bearing had seized on whichever wheel came off.

I replaced the standard Serpent wheel bearing with after market ones and the problem has never reaccured.

[Dom]

Thanks folks. Lots of good feedback.

The track runs clockwise, so it's the outside wheel (the majority of the time).

I've tried flanged nuts (as supplied with the kit) and these are serrated so they should be holding it. I've also tried a nylock nut (albeit an old one), but same result. And I've tried putting these on with as much force as I dare apply (I'm fairly strong so can apply as much torque as I want I guess...)

So I've ordered some brand new nyloc nuts AND some spring washers.
Together they are 4.2mm deep, so the nyloc should grab the stub axle.
With the spring washer as well, I'd be surprised if the wheel unscrewed itself ever again!

In the meantime, I'll check the hexes and the bearings carefully for any signs of wear/failure.

I have had another suggestion, that it might be a worn thread on the stub axle. Problem is I don't think anyone is 100% sure they've solved it as we now have a few people with a few different solutions. Not unless there are several different causes of this, with the same outcome (unlikely to my mind).

Suppose I'll have to approach this like setup - change one thing at a time...

Cheers everyone.

[shawn]

I have two cars and periodicly both have suffered with loose wheel nuts.

Last winter on the carpet, car 2 suffered all meeting with one wheel coming off and on closer inspection the hex had obviously been spinning inside the rim causing the nut to undo itself. The wheels (Sorex) had previously been on a Schumacher so I put it down to them being worn.
After fitting new wheels the problem never re-ocurred until...

Three weeks ago the same car suffered badly but this time everything looked ok, after assuming the hex was slipping again???
However my son had been putting additive on himself at the meeting so I kind of blamed him especially as nothing else appeared to be causing the problem. Perhaps he was inadvertantly loosening/undoing the nuts when rotating the wheels?
Never the less and not 100% confident, the problem didn't happen again at the following meeting when making sure the wheels were being rotated clockwise.

Last week after stripping car 1 down after the last meeting I noticed the right hand front wheel nut was "just" holding on by it's last couple of threads...! I was really fortunate here because I had had such a brilliant and satisfying meeting for once.

Now putting the cause down to the serrated nuts perhaps chewing the rims up so that they no longer grip the plastic, I have now fitted thin 4mm (Fastrax) nylocks on both of the cars; so I guess time will tell. Particularly as some of you say you are already using them and still having issues.

To be continued :confused:

[Dom]

Can I ask if everyone who is experiencing wheel nuts slackening, are they running the same components?

I run a spool up front, solid layshaft (no one-way pulley in there) and a gear diff at the back. I don't suppose whether it's gear diff or ball diff at the back is important. I mention it for completeness.

I suspect this is just about the amount of force going through the front, without a diff action to counter the forces.

I think it must be the braking force unscrewing the left hand wheel. There are 3 points on our track at Stonehaven where we have to brake hard and late.

If someone has a one-way up front or on the layshaft, and still losing wheel nuts, I'd like to know. And is it always left, always right or either...

[stok217]

if you no what impact glue is i use that on the iside of a wheel nut then screw it on
let the glue dry and it will stay on but the best bit :D is that you can unscrew the nut back off

[shawn]

Can I ask if everyone who is experiencing wheel nuts slackening, are they running the same components?

I run a spool up front, solid layshaft (no one-way pulley in there) and a gear diff at the back. I don't suppose whether it's gear diff or ball diff at the back is important. I mention it for completeness.

I suspect this is just about the amount of force going through the front, without a diff action to counter the forces.


Both my cars are completly kit standard.

[paul.upton]

im not sure what else to suggest to you, i am running kit stub axles, kit hexes and kit wheel nuts with no problems!! not even had a hint of wheels coming loose!!

other then changing the stub axles, maybe try changing them front to back as there is less stress on the back??

Paul

[GWESTY]

hi , when i tested the car indoors in jan/feb
i/we had these issues , the answer was the wheel
hexes ! the kit ones are shamfered so i changed the
front pair to non shamfered .
serpent do stock these
glenn

[neffy]

Hi we run a s400 in modified and have never had a wheel nut come loose since changing to RCcore serated ones and also just check your pins in the hexes are fully located by putting a wheelnut on and then tighten up hex . Hope this helps.

[Woodchop]

A dab of superglue adds re-assurance,and also takes up any slop there may be in relation to axle/nut fit.:)

[tc3team]

You could also try lightly scoring the plastic of around the driveshaft hole of the wheel with a small screwdriver, going in several lines from the hole outwards, 8 lines should be enough per wheel.
If the wheel nut is smooth on the inside and the wheel surface is smooth when it clamps up to the nut I found on my ta05 with a spool they kept coming undone until i did this and I was only racing stock!

I noticed it more probably because I had just replaced all the wheel nuts to blue alloy ones and replaced wheels.

[Dom]

Solved my particular problem. CVD joint was a little loose - pin wasn't centered.
At high speed (throttle on) and a lot of steering lock applied, the inside wheel was chattering badly.
Rebuilt the CVDs and wheels stayed put (but still slight vibration).

I've since decided to start balancing the completed tyres & wheels. I'm surprised that almost all tyres I have (old and new) need some adjustment.

I'll be use a aircraft prop balancer and will experiment with different materials for adding weight.

[terryh]

Try using using Blu-tac for balancing, works really well.

[kschu]

how to balance wheel using blue tac?

thanks

[terryh]

how to balance wheel using blue tac?

thanks

You will first need a balancer such as the MuchMore Racing do a multi wheel balancer, but a aircraft prop balancer will also do the trick. When you spin the wheel on the balancer the heavy side of the wheel will always fall to the bottom, stick a piece of blu-tac directely opposite and spin the wheel again, repeat as necessay.

[slow coach]

had same problem last meeting on inspection later i noticed the cvd pin had also come loose, i have since ground a flat on the pin to give the grub screw a good point of contact, im hoping this wont happen again